The Synthesis And Catalytic Properties Of N-Heterocyclic Palladium Ionic Salt

Coupling reaction is always mainly one of the methods of formating C-C, C-N bond. Because Suzuki Coupling reaction has much advantages:mild reaction conditions, a wide range compatibility on the functional group, little influence by the steric hindrance, arylboronic acid easily obtained and so on. Suzuki reaction has already become a first choice on the synthesis of natural products, drugs and other materials.In recent years, N-heterocyclic carbenes ligands have gradually aroused extensive attention for its unique properties and were applied in a variety of palladium catalyzed reactions.A series of N-heterocyclic carbenes ligand were designed and synthesized in this paper. And we research the ligands affect palladium as catalysts catalyze Suzuki crossing-coupling reactions. At first, we synthesized imidazole carbene salts by literature; then we obtained N-heterocyclic carbenes ligand 3a-e by "click" reaction with the imidazole carbenes salts and azide.The influence of catalytic activity of the ligands on Pd-catalyzed aryl bromide Suzuki reaction was studied. The influence of Pd source, base, solvents, Pd/3 molar ratio, Pd/S molar ratio and so on were studied,too.The optimum conditions were DMF/H2O-K2CO3, a little water, Pd/3b (1:1). At the optimum conditions, the reaction results showed the yield of most aryl bromide above 90%, the highest yeild up to 99%.The yeild of all the five ligands were up to 75% in the Pd-catalyzed aryl bromide Suzuki reaction with benzyl bromide and phenylboronic acid.At the same time, N-heterocyclic functional ionic liquid was synthesized by the similar method, the coordination compounds were synthesized by ionic liquid with palladium acetate. The coordination compounds as catalyst was used in olefin hydride addition reaction, and researched the catalytic cycle of application systems, the reaction results showed that catalytic systems can be reused many times.Under the mild reaction conditions, the catalysts had a very well activity for hydrogenation of different types olefins, the activity did not decline when the catalysts used multiple cycles. The result showed the correct structure of the ligands and ionic liquids synthesized in this paper by NMR, IR and elemental, all Suzuki coupling products were detected through magnetic resonance.